Trialkyl lead selenides



Patented Nov. 28, 1961 3,010,980 TRIALKYL LEAD SELENEES Wallace Richardson, Lafayette, Calif, assignor to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Filed Sept. 30, 1960, Ser. No. 59,510 3 Claims. (Cl. 260-437) This invention relates to a novel organometal compound. More particularly, the invention is concerned with a class of superior new lead selenide antiknock compounds for hydrocarbon fuels of the gasoline boilmg range.

Gasoline compositions of high octane number are commonly required for modern spark ignition internal combustion automobile and aircraft engines. Engines of these types in general use today are designed with high generally realized that there is at present a limit to the improvement in octane number that can be obtained by such conventional methods and additives. New gasoline base stocks with the combination of diiferent additives are greatly needed, therefore, to avoid present limitations and provide gasoline compositions of high octane number for future use in automobile and aircraft englnes.

It has now been foundthat a superior new gasoline composition of high octane number is provided by a hydrocarbon base fuel boiling in the gasoline boiling range, containing trialkyl lead selenide, preferably, trimethyl lead methyl selenide or trimethyl lead phenyl selenidc, a novel and more effective class of lead compounds, in amounts suflicient to improve the octane number, preferably, at least 0.5 milliliter per gallon of base fuel.

The improved gasoline compositions containing the new antiknock compound of the invention show unexpectedly high octane numbers compared to previously known combinations of hydrocarbon base fuels and additives. Hydrocarbon base fuels, together with trialkyl lead selenides and mixtures thereof in accordance with the invention, have octane numbers which are higher than similar base fuels employing the conventional lead tetraethyl additive in the same lead content. This is surprising since it has been generally accepted hereto fore that other lead compounds are distinctly less efficient than lead tetraethyl with respect to octane number improvement.

The hydrocarbon base fuel of the composition, according to the invention, is prepared by conventional refining and blending processes. It normally contains straight-chain paraffins, branched-chain parafiins, olefins, aromatics and naphthenes. Since straight-chain paraffins have a tendency to adversely affect octane number, the content of such hydrocarbons is ordinarily low.

As already mentioned, the base fuel is a hydrocarbon fuel boiling in the gasoline boiling range. Generally described, such fuels have an ASTM (D-86) distillation with an initial boiling point of about 100 F. and a final boiling point of about 425 F. Preferably, the unleaded base fuel has a Research octane number of at least 85 as determined by the accepted CFR engine test method. Also, the base fuel preferably contains at least 20 percent by volume of aromatic hydrocarbons. Less than 30 percent by volume of olefinic hydrocarbons are present in the fuel. The total paraffin and naphthene hydrocarbon content of the preferred fuel may be as much as percent by volume. For best over-all engine performance, fuels containing in the range of 20 to 60 percent by volume of parafiinic and naphthenic hydrocarbons are preferred for volatility andother desirable gasoline characteristics. The more preferred hydrocarbon base fuels are also those which contain from 20 to 60 percent by volume aromatic hydrocarbons and from 0 to 30 percent by volume of olefinic hydrocarbons. Most preferably, a gasoline having all-around desirable characteristics has a clear octane number of at least and contains about 50 to 60 percent by volume of paraffin and naphthene hydrocarbons, about 30 to 40 percent aromatic hydrocarbons and about 5 to 15 percent olefinic hydrocarbons.

The trialkyl lead selenides are illustrated by the general formula in which the R s are alkyl groups and R is a hydrocarbon radical. The trialkyl lead selenides preferably contain from one to three carbon atoms in each of the alkyl groups attached directly to the lead. The alkyl groups may be the same or different from one another. Particularly preferred for antiknock performance are the trimethyl lead methyl or phenyl selenides.

For practical purposes, not more than about 4 milliliters of lead compounds per gallon is ordinarily used in the compositions. If desired, other octane-improving additives may be employed in addition to trialkyl lead selenide. These include other lead compounds such as lead tetraethyl, carbonyl derivatives of iron and cyclopentadienyl derivatives of metals such as manganese or iron. Other gasoline additives, such as scavengers like ethylene chloride or bromide, oxidation inhibitors, corrosion inhibitors, surface ignition suppressants like phosphorus compounds, detergents, and the like may be present.

The following examples illustrate the preparation of trialkyl lead selenide compounds in accordance with this invention. Unless otherwise specified the proportions are on a Weight basis.

Example I This example shows the preparation of trimethyl lead,

methyl selenide. One-half mole of methyl magnesium bromide is treated with one-half mole of powdered selenium. The resulting intermediate methyl selenomagnesium bromide is treated directly with one-half mole of trimethyl lead chloride. A mildly exothermic reaction occurs, and the mixture is rapidly stirred and refluxed for one-half hour. An ice-cold solution of ammonium chloride is added to remove the magnesium salts, and the seleno-lead compound is extracted with ethyl ether. The extract is dried and the other is removed in vacuo at room temperature. The isolated product is a yellow oil obtained in a yield of 50 percent based on selenium. The boiling point is 75 C. at a pressure of 3 mm. of mercury and the compound boils with slight decomposition. The specific gravity at 20 C. is 2.42.

Example 11 This example shows the preparation of trimethyl lead phenyl selenide. A solution of 0.2 mole of phenyl magnesium bromide in 300 ml. anhydrous ethyl ether is treated with. 15 g. (0.18 mole) of finely powdered selenium. A vigorous reaction follows this addition, and the reaction is completed by refluxing the material for 3 one-half hour. Sixty-three grams (0.18 mole) of trimethyl lead chloride is added gradually. A very mild exothermic reaction occurs, and the mixture becomes dark brown. The materials are refluxed for 1 /2 hours. The magnesium salts are removed by treatment with an ice-cold solution of ammonium chloride, and the product is extracted with ethyl ether, dried over anhydrous magnesium sulfate, and the ether is removed under vacuum. The product is isolated as an orange-colored oil having a specific gravity of 2.60. The yield based on the selenium is 60 percent.

In further illustration of the superior new gasoline antiknock compound of the invention, several compositions and tests thereon are given in the following examples. These tests show the improved effect of the combination of the particular hydrocarbon base fuel with trialkyl lead selenide compounds as compared with fuels containing other lead compounds.

The following table is a summary of the pertinent data of the examples. The hydrocarbon base fuel has a Research octane of 94.4 and contains 51 percent by volume of the paraflins and naphthenes, 25 percent olefins, and 24 percent aromatics. The table shows the efiect on octane number by the addition of representative trialkyl lead selenides, as compared to lead tetraethyl. The octane numbers in this comparison are based on the Research Method D-'908 and the Motor Method D-357 of the ASTM'Manual of Engine Test Methods for Rating Fuels. The latter method, which is more stringent than the Research Method, illustrates more accurately the desirable qualities of the improved gasoline composition of the invention.

In the table, the effect of trialkyl lead selenide compared with lead tetraethyl is based on gasoline compositions containing an equal lead concentration. For the purpose of practical comparison this is 3.17 grams of lead per gallon. Such amounts are equivalent to the 3 cc. of tetraethyl lead per gallon employed in many gasolines. The improvement is the difierence in the octane number obtained with trimethyl lead seleno compound less the octane number obtained with the equivalent amount of lead tetraethyl.

Table Example Lead Compound Research Improve- Motor Improve- N o. Octane ment Octane ment III Tetraethyl Lead 99.2 87.7 IV Trimethyl lead I,

' phenyl selenide. 99. 4 +0. 2 88. 2 +0. 5 V. Trimethyl lead methyl selenide. 99. 5 +0. 3 88. 0 +0. 3

The examples summarized in the above table show that the improved gasoline composition of the invention containing trialkyl lead selenide is surprisingly better on .the basis of octane number rating than comparable gasoline compositions of the type known heretofore.

The organolead compounds of this invention are also useful wherever oil-soluble lead compounds are desired. For example, fine particle dispersions of lead may be obtained by thermal decomposition of the trialkyl lead selenide dissolved in liquid hydrocarbon, such as isooctane. Such fine metal dispersions of lead are useful as catalysts for certain reactions. The fine lead particles may be converted to lead oxides which are useful as lubrication agents. The lead compound of the invention may also be used as a free radical initiator in polymerization reactions.

I claim: 1. Trialkyl lead selenides of the formula R,i bse12,

l in which R is methyl and R is selected from the group consisting of methyl and phenyl.

2. Trimethyl lead phenyl selenide. 3. Trimethyl lead methyl selenide. 

1. TRIALKYL LEAD SELENDIDES OF THE FORMULA 